The local user (potentially not logged in).

Until the user logs in or authenticates himself the profile data will be invalid and no other Social API functionality will work.

//JavaScript
Social.localUser.Authenticate (function (success) {
        if (success) {
            Debug.Log ("Authentication successful");
            var userInfo : String = "Username: " + Social.localUser.userName + 
                "\nUser ID: " + Social.localUser.id + 
                "\nIsUnderage: " + Social.localUser.underage;
            Debug.Log (userInfo);
        }
        else
            Debug.Log ("Authentication failed");
    });

//C#
Social.localUser.Authenticate (success => {
		if (success) {
			Debug.Log ("Authentication successful");
			string userInfo = "Username: " + Social.localUser.userName + 
				"\nUser ID: " + Social.localUser.id + 
				"\nIsUnderage: " + Social.localUser.underage;
			Debug.Log (userInfo);
		}
		else
			Debug.Log ("Authentication failed");
	});